


Mounting Anxiety

by magisterpavus



Series: Sheith Centaurs AU [2]
Category: Voltron: Legendary Defender
Genre: Alternate Universe - Fantasy, Centaurs, Cuddling & Snuggling, First Time, Fluff and Humor, Intersex Keith (Voltron), M/M, Sexual Tension, Size Difference, Soulmates, centaur sex that's what this is ok
Language: English
Status: Completed
Published: 2020-04-18
Updated: 2020-04-18
Packaged: 2021-03-01 19:54:13
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,402
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23722675
Author URL: https://archiveofourown.org/users/magisterpavus/pseuds/magisterpavus
Summary: Shiro struggles to get used to his new, strange,largecentaur body.Thankfully, Keith is very supportive.
Relationships: Keith/Shiro (Voltron)
Series: Sheith Centaurs AU [2]
Series URL: https://archiveofourown.org/series/1708660
Comments: 33
Kudos: 536





	Mounting Anxiety

**Author's Note:**

> It may be helpful to read the first part in this series to get some background on what's happening here, but if you're just here for the centaur fucking, I respect that, and you probably won't be too confused. but here's a summary for context:
> 
> tldr; in part 1 keith turned shiro into a centaur (also called galra here) to save his life and they turned out to be soulmates because ofc they did
> 
> anyway, here's Shiro having a crisis over his horse dick :|

Shiro is, of course, grateful to be alive. 

He’s grateful to Keith for performing the spell, grateful that the spell worked, and grateful that his illness is cured. When he was sick, he hadn’t hesitated because his form would change – it was a small price to pay for having a second chance at life. Honestly, he found the idea novel and exciting at the time – few had the chance to change the body they were born in, after all, and even fewer so drastically.

The truth is that Shiro foolishly thought he knew exactly what he was signing up for when he agreed to let Keith turn him into a centaur.

But the reality is that nothing could have prepared Shiro for being turned into a horse from the waist down. Keith reminds him it’s not  _ really  _ a horse, centaurs are their own thing, but Shiro’s brain still says  _ horse,  _ and it’s fucking him up a little. 

Not in a bad way, necessarily. It’s just _ new.  _ It’s overwhelming to suddenly be a head taller than Keith, and to be aware of just how massive his new body is. He was self-conscious of his thunderous hoofsteps for weeks, and still feels like a lumbering beast next to Keith sometimes, with his much daintier stride and build. Not that Keith isn’t also massive. All centaurs are big; Keith is easily seven feet tall from hoof to head. 

It’s just – Shiro’s big even for a centaur. He’s painfully aware of this fact. Every time other centaurs visit their hut for healing poultices or bandages or a little of Keith’s magic, their gazes linger on Shiro with marked surprise. Even Krolia, who is larger than most of the lowland Galra, doesn’t quite measure up. She’s never looked upon him with surprise though – more like knowing approval. Shiro finds himself very flustered and confused by the attention.

Keith hasn’t commented on it, not really. After Shiro was transformed and they both heard their Chimes as their soulmarks aligned, they spent the night curled together, their arms around each other. Shiro had held Keith so tightly, and Keith had nuzzled into his throat, kissing his glowing soulmark with soft, sweet sounds, and Shiro swore there was nothing so perfect as that first night together.

The next day, Keith taught Shiro how to run on four legs. It was, to put it lightly, a bit of a disaster – there were more than a few tumbles into the brush, and Shiro learns very quickly that weighing over a thousand pounds makes for quite a lot of destruction when he smashes into things. Once he gets the hang of it, though – the feeling of galloping beside Keith through the sunny woods is indescribable. 

Keith is faster, more practiced and agile when they chase each other on slow afternoons, but Shiro quickly learns he has the greater stamina of the two of them, and can never quite feel guilty about running Keith down to exhaustion when at last he catches him in the rolling hills and they both go tumbling down into the laughing brook, their own laughing echoing far and wide. Those are good days, when Shiro rolls onto his back and kicks up all four hooves to the sky in such an ungainly way that Keith laughs harder, and rolls into his side, burying his giggles in Shiro’s now-dusty black pelt and flicking his tail in amusement against Shiro’s flanks. 

Keith’s good at hiding his thoughts and emotions, though. When not laughing and wrestling with him, he is quiet and more than a little enigmatic. Part of it, Shiro suspects, may be the gap in body language between them – he surely doesn’t pick up on every little cue, so for all he knows, Keith is a talkative centaur. 

But sometimes Shiro catches Keith eyeing him when he thinks Shiro isn’t looking, and he’s never sure if it’s an approving or critical look. It makes him even more uncertain. Maybe Keith is having second thoughts. Maybe he only liked Shiro as a human, when he was smaller and piqued Keith’s curiosity.

They just haven’t... _ done  _ anything with each other, not since their Chimes, and this troubles Shiro. According to what Keith told him, after the Chiming, or during it, they’re supposed to mate. But Keith never initiated anything, nor suggested Shiro should. He seems content to nuzzle and kiss and keep his distance from anything below the still-humanoid torso, so Shiro doesn’t dare to push further. He was raised human, not centaur – he doesn’t know how this works. Do centaurs just mate to mate? Is it ever recreational? Do they have foreplay? 

These are things Shiro has learned to think about carefully and sparingly, only when he’s alone, because he’s learned that it’s much, much harder – _ ha  _ – to hide his arousal in this new form. The first time he figured  _ that  _ out, he was watching Keith from across their little garden, gaze lingering on the flex of his back as he reached up to pluck an apple from a low-hanging branch. 

In the sunshine, his skin looked warm and soft, lean muscles rippling, and it was strange, but even the dark red shine of his coat did something for Shiro. Something in his hindbrain whispered,  _ healthy, strong, pretty, mine, _ and that was all it took for Shiro to realize with a start that the organ he’d been trying  _ very hard to ignore  _ was hanging heavy between his hind legs, slipping slow and inexorable from its sheath. 

With a weak excuse, Shiro ran away. He’s not proud of that, but all logic had been clouded with shame and blinding want, and as soon as he was out of Keith’s sight, he forced himself to stand in a cold pond for what could have been hours until the disconcerting sensation passed. There are some things he’s not sure he’s ready to deal with yet, and his horse dick is one of them.

_ Not a horse dick, _ Keith would say.

But Shiro’s pretty sure it’s basically a horse dick. Admittedly, he’s looked as best he can, with a mixture of fear and fascination. Shiro’s no expert, but the resemblance is undeniable, except that centaurs are bigger than horses. Somehow. 

When it finally happens, it’s a complete accident. 

They’re snuggled together in Keith’s cot on the floor, which they’ve since expanded to fit the two of them, and Shiro is tucked along his back, nosing at the nape of his neck. Keith smells like the medicinal herbs he uses throughout the day, but also lingering cookfire smoke and something sharp and sweet, honeyed and irresistible. Shiro sighs, eyes falling shut in simple pleasure, only to fly open in horror when Keith shifts, clears his throat, and whispers, “Do...do you want to mount me?”

Shiro scrambles back as best he can with one arm and four hooves, which is to say very awkwardly. Sure enough, his dick is out and nudging at Keith’s flank, speckled black and pink and flopping in a terribly unwieldy way out of its sheath which is not doing its damn job. Unfortunately, Keith is not shyly averting his gaze. No – he’s staring straight at it with an assessing eye, then glancing back up at Shiro, brow raised as if to say,  _ Well? What are you waiting for? _

Shiro opens his mouth, then closes it. “I,” he croaks, and covers his face with his hand. “Keith. I don’t know what I’m doing, here.”

Keith makes a soft sort of crooning sound, and  _ fuck,  _ that does nothing to convince his dick it should go back where it came from and never return. “Hey,” Keith murmurs, twisting around and sitting up so he can cup Shiro’s face. His expression is fond and his smile is equal parts amused and kind. “Don’t worry. I know this is...strange, for you. But it will feel good for us both, I think.” Keith chuckles, ducking his head. “This is new for me too, remember?”

Shiro wets his lips. “Oh,” he whispers. His hips give a little, involuntary kick, and Keith’s smile widens. “Then...you want me to…”

“Mount me?” Shiro turns bright red and Keith laughs again. How easily he says that. “Yes, Shiro,” Keith says, and his voice drops a little, his hand stroking down Shiro’s jaw and over the swell of his chest. “I’ve been hoping you would for a while, now.”

_ “Oh,”  _ Shiro squeaks, and struggles to stand as Keith does, the two of them circling each other in the hut – or rather, Keith circles Shiro, because Shiro’s honestly too big to move much in the small space. “I – I was worried that maybe I was too. Um. Large.”

Keith pauses, his eyes widening in disbelief. “Shiro,” he says, slowly, “is large size not appealing among humans?”

Shiro stammers around an answer. “Well – I mean, yes, but –”

Keith cuts him off. “Good,” he drawls. “It is the same among Galra. Shiro, I find your size very appealing. I want you to fill me. Please. Or would you have me beg?”

Shiro stamps his front hoof and doesn’t even realize he’s doing it until Keith glances down with a smirk. “That’s what I thought,” Keith says, and stops his circling squarely in front of Shiro, looking back at him as his black tail flicks up and away. Shiro stares, unable to register what he’s seeing. There’s the dark pucker of Keith’s hole, which he expected even if he’s never seen, but beneath it – 

“You’re –” Shiro stops, his cock dripping at the sight of it, enfolding the last few heavy inches from its sheath as his eyes trace over dark, engorged folds, the hint of wetness within, waiting for him. 

Keith shrugs, like it’s nothing. “Galra have more than two sexes,” he says. “Have you never wondered what that potion is that I take every morning? It is so I cannot be bred.” He watches Shiro with a kind of slyness that only serves to make Shiro’s blood run hotter. “I have no desire to foal, though you are welcome to do your worst.”

_ “Keith,”  _ Shiro hisses through his teeth, frantic. He still doesn’t fully understand what’s driving him forward, what’s making him so dizzy and eager to do exactly what Keith’s asking – or perhaps demanding – of him, but he knows he wants it. He’s always wanted Keith, after all, human or not.

Keith hums, rolling his shoulders and glancing at Shiro over his shoulder, tail still lifted. “I’m waiting.”

When Shiro moves, it’s more instinct than conscious thought. He surges up onto Keith, front legs braced on either side of his back and hand pressing down over Keith’s withers as his hips buck forward desperately and his cock catches against shocking heat. Shiro growls in frustration – the angle is bad, neither of them can reach to guide him in, and Shiro curses Nature for doing things this way...at least until the flared crown of his cock finds purchase and slides deep, and he immediately rescinds all complaint in favor of overwhelming bliss. Keith takes him beautifully, and Shiro forgets his previous trepidation. 

Under him, Keith moans, head falling forward and hair falling into his face, and in reply, Shiro makes the same sound Keith first did – a low, soothing croon. He reaches out to draw Keith’s head to his and kisses him, greedy and sloppy, licking into his mouth as his hooves scrabble briefly astride Keith before he starts to move, and once he starts, he can’t stop. 

It’s different from when he was human – it’s  _ more, _ a kind of itch under his skin he needs to scratch, an insistent urge to fuck Keith hard enough to verge on violence, relentless in the rutting of his cock inside Keith’s hot cunt. Keith’s legs shake, struggling to stay upright under the onslaught, under Shiro’s massive weight bearing down fully over him, and with a growl Shiro remembers Keith’s cock – he can’t reach it at all from this angle, and that won’t do.

With no real assurance that it’s going to work, Shiro shoves at Keith’s back and Keith cries out under him, hooves shuffling, tightening around Shiro’s cock like he’s afraid he’s going to leave. Shiro croons again and murmurs, “Lay down, on your side; I want to touch you.”

Keith makes a noise of confusion, eyes bleary, but nods, whimpering when Shiro backs off, his cock swinging free, but only for a few moments. Keith half-collapses on his side in their bed and Shiro shuffles up behind him, grunting in frustration until he manages to tuck his legs in enough to press himself flush to Keith and thrust in again, this time with one of his legs tangled with Keith’s and the other shoved between Keith’s hind legs, nudging at his cock, giving him a sweet slide of friction. 

Clearly Keith did not expect this, because he throws his head back, gasping incoherently as Shiro fucks into him. He can’t do so with quite as much power as before, but Shiro doesn’t mind – it’s better like this, snuggled up to Keith, able to hold him and focus less on keeping his balance, more on making it good for him. Shiro wants, so badly, to be good for him.

It must work out alright, because it isn’t long after that before Keith groans and shudders under him, milking his cock in shaky spasms as his own cock spills in hot splashes all over the reeds and blankets. Shiro buries his face in Keith’s shoulder, arm wrapped tight around his chest, pulling Keith to him as he follows him over the edge, hips bucking through climax, cock pulsing again and again, flooding Keith’s pliant body with waves of sticky heat as they both relax into the bedding. Shiro’s cock doesn’t seem to want to go anywhere anytime soon, and when he peers between them, he feels it twitch hard in another ripple of climax at the sight of frothing rivulets dripping out along glistening folds, staining Keith’s pretty red coat with silver. 

They pant quietly together in the aftermath, and then Keith giggles. Shiro lifts his head, blushing, and nudges him. “What? What is it?”

Keith shakes his head, his smile crooked and goofy. “Nothing,” he chuckles. “You just make a very good stallion.”

Shiro groans at him in embarrassment, and Keith laughs louder, the sound bright and joyful in their now very musky hut. 


End file.
